1. Field of the Invention
The subject invention relates to an axle assembly having a dual wheelend at each end of an axle shaft in which one wheel hub is permitted to rotate relative to the other wheel hub.
2. Description of Related Art
Axle assemblies having dual wheelends on both ends of an axle shaft have been used to increase the load bearing capability of trailers and heavy duty vehicles. Typically, the pair of wheels on each end of the axle assembly are secured together such that each pair of wheels rotates together as a unit.
Some of the dual wheelends for the heavy duty vehicles are driven and are therefore more complex and more difficult to design. Further, some of the heavy duty vehicles, such as lift trucks, undergo numerous turning maneuvers which produces significant wear on the tires. Specifically, the wear on the tires occurs when at least one of the tires scrub, or drag, during a turn. This phenomenon occurs because, although the tires are secured together, the tires must travel different distances at the inside and outside of the turning radius. Tire wear and maintenance on heavy duty lift trucks due to scrub creates a significant yearly cost to the user of these vehicles.
Dual wheelends have been developed that permit each wheel hub to rotate relative to each other to reduce scrubbing during vehicle turns. Also, such as disclosed in U.S. Pat. No. 6,419,325, some of these dual wheelends are designed to drive one of the wheel hubs. Certain driving conditions require that both of the wheel hubs be driven to provide enough traction to propel the heavy vehicle. There have been dual wheelends developed to satisfy this need and these dual wheelends typically utilize a differential mechanism disposed between the wheel hubs such that both wheel hubs may be driven at the same rate when the vehicle travels in a straight path. The differential mechanism permits the wheel hubs to rotate relative to each other when the vehicle travels in a curved path to reduce scrubbing. Examples of driven dual wheelends with differential mechanisms are disclosed in U.S. Pat. Nos. 6,254,193 and 6,471,301.
Although driven dual wheelends have been contemplated, there remains a need to develop a commercially viable design that can withstand the rigors of use and that incorporates all of a customer's desired features. Further, driven dual wheelends experience significant loads during operation and a design must be developed to support and/or transfer these loads away from the wearable components of the wheelend.